The proposed work involves the design, synthesis, and conformational analysis of model peptides whose structures are chosen so that they might elucidate basic biophysical questions of current interest. For example, we are using a series of cyclic pentapeptides to study the relationship between amino acid sequence and preferred reverse-turn conformations. This series also serves as a model to probe the stability of various hydrogen bonds and the nature of solvation of peptides, as well as to provide spectral parameters which may be referred to in studies of more complex and often flexible natural peptides. Other areas of focus are the influence of a membrane environment on peptide conformation and the interactions of peptides with ions. Nuclear magnetic resonance and circular dichroism are the principal tools used for conformational analysis.